switch the control signal of DRV8812s

Hi Team,

I would like to have your advice.

My customer considers to use two DRV8812s for his application.
The block diagram that he images is like the following.


I heard Motor_A and Motor_B are operated alternatively but one have to "hold the previous state" when the other is operated.
He assumes switching the control signal of DRV8812s and is having think how to design the "Selector" above.
Do you have any idea for the the schemaic of "Selector" above?
He wants low cost and low space solution.

Best regards,
Yaita / Japan disty